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  <h1>The Mesa 3D Graphics Library</h1>
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<h1>Compilation and Installation using Meson</h1>

<h2 id="basic">1. Basic Usage</h2>

<p><strong>The Meson build system is generally considered stable and ready
for production</strong></p>

<p>The meson build is tested on Linux, macOS, Cygwin and Haiku, FreeBSD,
DragonflyBSD, NetBSD, and should work on OpenBSD.</p>

<p><strong>Mesa requires Meson >= 0.45.0 to build.</strong>

Some older versions of meson do not check that they are too old and will error
out in odd ways.
</p>

<p>
The meson program is used to configure the source directory and generates
either a ninja build file or Visual Studio® build files. The latter must
be enabled via the <code>--backend</code> switch, as ninja is the default backend on all
operating systems. Meson only supports out-of-tree builds, and must be passed a
directory to put built and generated sources into. We'll call that directory
"build" for examples.
</p>

<pre>
    meson build/
</pre>

<p>
To see a description of your options you can run <code>meson configure</code>
along with a build directory to view the selected options for. This will show
your meson global arguments and project arguments, along with their defaults
and your local settings.

Meson does not currently support listing options before configure a build
directory, but this feature is being discussed upstream.
</p>

<pre>
    meson configure build/
</pre>

<p>
With additional arguments <code>meson configure</code> is used to change
options on already configured build directory. All options passed to this
command are in the form <code>-D "command"="value"</code>.
</p>

<pre>
    meson configure build/ -Dprefix=/tmp/install -Dglx=true
</pre>

<p>
Note that options taking lists (such as <code>platforms</code>) are
<a href="http://mesonbuild.com/Build-options.html#using-build-options">a bit
more complicated</a>, but the simplest form compatible with Mesa options
is to use a comma to separate values (<code>-D platforms=drm,wayland</code>)
and brackets to represent an empty list (<code>-D platforms=[]</code>).
</p>

<p>
Once you've run the initial <code>meson</code> command successfully you can use
your configured backend to build the project. With ninja, the -C option can be
be used to point at a directory to build.
</p>

<pre>
    ninja -C build/
</pre>

<p>
Without arguments, it will produce libGL.so and/or several other libraries
depending on the options you have chosen. Later, if you want to rebuild for a
different configuration, you should run <code>ninja clean</code> before
changing the configuration, or create a new out of tree build directory for
each configuration you want to build
<a href="http://mesonbuild.com/Using-multiple-build-directories.html">as
recommended in the documentation</a>
</p>

<dl>
<dt><code>Environment Variables</code></dt>
<dd><p>Meson supports the standard CC and CXX environment variables for
changing the default compiler, and CFLAGS, CXXFLAGS, and LDFLAGS for setting
options to the compiler and linker during the initial configuration.

These arguments are consumed and stored by meson when it is initialized. To
change these flags after the build is initialized (or when doing a first
initialization), consider using <code>-D${lang}_args</code> and
<code>-D${lang}_link_args</code> instead. Meson will never change compiler in a
configured build directory.
</p>

<pre>
    CC=clang CXX=clang++ meson build-clang
    ninja -C build-clang
    ninja -C build-clang clean
    meson configure build -Dc_args="-Wno-typedef-redefinition"
    ninja -C build-clang
</pre>

<p>
The default compilers depends on your operating system. Meson supports most of
the popular compilers, a complete list is available
<a href="http://mesonbuild.com/Reference-tables.html#compiler-ids">here</a>.
</p>

<p>Meson also honors <code>DESTDIR</code> for installs</p>
</dd>


<dt><code>LLVM</code></dt>
<dd><p>Meson includes upstream logic to wrap llvm-config using its standard
dependency interface. It will search <code>$PATH</code> (or <code>%PATH%</code> on windows) for
llvm-config (and llvm-config$version and llvm-config-$version), so using an
LLVM from a non-standard path is as easy as
<code>PATH=/path/with/llvm-config:$PATH meson build</code>.
</p></dd>
</dl>

<dl>
<dt><code>PKG_CONFIG_PATH</code></dt>
<dd><p>The
<code>pkg-config</code> utility is a hard requirement for configuring and
building Mesa on Unix-like systems. It is used to search for external libraries
on the system. This environment variable is used to control the search path for
<code>pkg-config</code>. For instance, setting
<code>PKG_CONFIG_PATH=/usr/X11R6/lib/pkgconfig</code> will search for package
metadata in <code>/usr/X11R6</code> before the standard directories.</p>
</dd>
</dl>

<p>
One of the oddities of meson is that some options are different when passed to
the <code>meson</code> than to <code>meson configure</code>. These options are
passed as --option=foo to <code>meson</code>, but -Doption=foo to <code>meson
configure</code>. Mesa defined options are always passed as -Doption=foo.
</p>

<p>For those coming from autotools be aware of the following:</p>

<dl>
<dt><code>--buildtype/-Dbuildtype</code></dt>
<dd><p>This option will set the compiler debug/optimisation levels to aid
debugging the Mesa libraries.</p>

<p>Note that in meson this defaults to <code>debugoptimized</code>, and
not setting it to <code>release</code> will yield non-optimal
performance and binary size. Not using <code>debug</code> may interfere
with debugging as some code and validation will be optimized away.
</p>

<p> For those wishing to pass their own optimization flags, use the <code>plain</code>
buildtype, which causes meson to inject no additional compiler arguments, only
those in the C/CXXFLAGS and those that mesa itself defines.</p>
</dd>
</dl>

<dl>
<dt><code>-Db_ndebug</code></dt>
<dd><p>This option controls assertions in meson projects. When set to <code>false</code>
(the default) assertions are enabled, when set to true they are disabled. This
is unrelated to the <code>buildtype</code>; setting the latter to
<code>release</code> will not turn off assertions.
</p>
</dd>
</dl>

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